<?php
/**
 * Copyright 2011 Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License. You may obtain
 * a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

require_once "base_facebook.php";

/**
 * Extends the BaseFacebook class with the intent of using
 * PHP sessions to store user ids and access tokens.
 */
class Facebook extends BaseFacebook
{
  /**
   * Identical to the parent constructor, except that
   * we start a PHP session to store the user ID and
   * access token if during the course of execution
   * we discover them.
   *
   * @param Array $config the application configuration.
   * @see BaseFacebook::__construct in facebook.php
   */
  public function __construct($config) {
    if (!session_id()) {
      session_start();
    }
    parent::__construct($config);
  }

  protected static $kSupportedKeys =
    array('state', 'code', 'access_token', 'user_id');

  /**
   * Provides the implementations of the inherited abstract
   * methods.  The implementation uses PHP sessions to maintain
   * a store for authorization codes, user ids, CSRF states, and
   * access tokens.
   */
  public function setPersistentData($key, $value) {
    if (!in_array($key, self::$kSupportedKeys)) {
      self::errorLog('Unsupported key passed to setPersistentData.');
      return;
    }

    $session_var_name = $this->constructSessionVariableName($key);
    $_SESSION[$session_var_name] = $value;
  }

  protected function getPersistentData($key, $default = false) {
    if (!in_array($key, self::$kSupportedKeys)) {
      self::errorLog('Unsupported key passed to getPersistentData.');
      return $default;
    }

    $session_var_name = $this->constructSessionVariableName($key);
    return isset($_SESSION[$session_var_name]) ?
      $_SESSION[$session_var_name] : $default;
  }

  protected function clearPersistentData($key) {
    if (!in_array($key, self::$kSupportedKeys)) {
      self::errorLog('Unsupported key passed to clearPersistentData.');
      return;
    }

    $session_var_name = $this->constructSessionVariableName($key);
    unset($_SESSION[$session_var_name]);
  }

  protected function clearAllPersistentData() {
    foreach (self::$kSupportedKeys as $key) {
      $this->clearPersistentData($key);
    }
  }

  protected function constructSessionVariableName($key) {
    return implode('_', array('fb',
                              $this->getAppId(),
                              $key));
  }
  
 /*
    Custom functions to get fan page related information
*/
function getSignedData()
{
    if(isset($this->signedData) && !empty($this->signedData))
        return $this->signedData;

    if(!isset($_REQUEST["signed_request"]))
        return false;

    $signed_request = $_REQUEST["signed_request"];

    if(empty($signed_request))
        return false;

    list($encoded_sig, $payload) = explode('.', $signed_request, 2);
    $data = json_decode(base64_decode(strtr($payload, '-_', '+/')), true);

    if(empty($data))
        return false;

    $this->signedData = $data;



    return $data;
}

/*
    Return fan page id, Only return fanpage id for 1st (landing) page of application.
*/
function getFanPageId()
{
    if(!$data = $this->getSignedData())
    {
        return false;
    }
    if(isset($data["page"]["id"]))
        return $data["page"]["id"];

    return false;
}

/*
    Only returns userid, if user has authenticated application
*/
function getFanPageUserId()
{
    if(!$data = $this->getSignedData())
    {
        return false;
    }

    if(isset($data["user_id"]))
    {
        return $data["user_id"];
    }

    return false;
}

/*
Check if visiting user is fan page admin
*/
function checkFanPageAdmin()
{
    if(!$data = $this->getSignedData())
        return false;

    if(isset($data["page"]["admin"]) && $data["page"]["admin"] == 1)
        return true;

    return false;
}

  
}
